Furnace construction with expansible muffle assembly



2 Sheets-Sheet 1 May 26, 1970 D. J. MORIN FURNACE CONSTRUCTION WITH EXPANSIBLE MUFFLE ASSEMBLY Filed Sept. 50, 1968 R N a m m m N O 0 W M 7H m A D M, L A N 0 3% GE 8 I l X l MQ Qh mm mm on m% r l *0 m 5 m mm j k I. D 5 0 J). Wu. V W I QVEW W A mm m w x w W A y 6 1970 D. J. MORIN 3,514,084

FURNACE CONSTRUCTION WITH EXPANSIBLE MUFFLE ASSEMBLY Filed Sept. 50, 1968 2 Sheets-Sheet 2 E [32: i K mmn'mrvxmrrn S4 :\\:\\\/'J H i: H

62 FIG.3 66

INVENTOR DONALD J. MORIN BY ATTORNEYS United States Patent Office 3,514,084 Patented May 26, 1970 3,514,084 FURNACE CONSTRUCTION WITH EXPANSIBLE MUFFLE ASSEMBLY Donald J. Morin, Plainville, Mass., assignor to S-M Engineering Corporation, North Attleboro, Mass., a corporation of Massachusetts Filed Sept. 30, 1968, Ser. No. 763,567 Int. Cl. F27]: 9/24; F27d 3/12 U.S. Cl. 263-8 7 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION In heat treating furnaces that incorporate a continuously moving conveyor and that have a mufile extending through the heating chamber thereof, the mufile is known to expand and contract due to temperature changes dur ing the operation of the furnace. In the conveyor type furnace known heretofore, the muflle was usually interconnected at the ends thereof to inlet and discharge ducts through which the conveyor extended. Since the muflle was bolted to the inlet and discharge ducts which were held in fixed position, expansion and contraction of the rnufile during the heat treating operation soon resulted in distortion of the metal from which the mufile was constructed, and thus after a period of time, the muflle eventually had to be replaced.

Some efforts have been made heretofore to compensate for the expansion and contraction of the muflle by providing for longitudinal movement of the inlet duct in some manner. Thus, as the 'mutfle expanded during the heat treating cycle, the expansion was compensated for, to some degree, by movement of the inlet duct therewith. However, the prior known construction that provided for longitudinal movement of the inlet duct was not adequate to fully compensate for the expansion and contraction of the mufile, and the muflle body was still subjected to undue stresses during the operation of the furnace. Furthermore, these stresses were particularly evident on the discharge end of the muflle since the discharge duct in the prior known constructions Was fixed, regardless of any provision that may have been established for allowing for movement of the inlet duct. Thus expansion and contraction of the mufile still occurred against the fixed discharge duct and fatigue of the muffle walls resulted after a period of use, which required replacement of the muffle within a relatively short preiod of time.

SUMMARY OF THE INVENTION The present invention relates to a heat treating furnace having a heating chamber through which a rnuflle extends in floating relation, the mufile being connected at the entry end thereof to an inlet duct and at the discharge end thereof to a discharge duct. In order to provide for the floating action of the muflle, the inlet and discharge ducts have rollers joined thereto that are received on fixed tracks. Since the inlet and discharge ducts are joined di-v rectly to the muflle, the entire mutfle assembly, in eifect, is located in floating relation and thus is adaptable for longitudinal movement in response to expansion and contraction of the mufile during the operation of the furnace. When the Inufile expands at the beginning of the heating cycle, the rollers joined to the inlet and discharge ducts provide for movement thereof in a longitudinal direction and, similarly, when the muflle contracts, the rollers compensate for this movement by reversely rolling on the tracks. Since the muflle is not subjected to undue stresses due to expansion and contraction thereof, the effective life of the mufile is materially increased.

DESCRIPTION OF THE DRAWINGS In the drawings which illustrate the best mode presently contemplated for carrying out the present invention:

FIG. 1 is an elevational view of the heat treating furnace construction embodied in the present invention;

FIG. 2 is an enlarged fragmentary elevational view of the stop construction as employed in one of the roller assemblies of the present invention;

FIG. 3 is a sectional view taken along lines 3-3 in FIG. 1; and

FIG. 4 is a reduced elevational view illustrating the floating position of the muffle assembly as interconnected to the inlet and discharge ducts.

DESCRIPTION OF THE INVENTION Referring now to the drawings and particularly to FIG. 1, a conveyor type heat treating furnace in which the present invention is incorporated is generally indicated at 10 and, as shown, the furnace 10 is constructed in the so-called humpback configuration. However, it will be understood that the concept of the invention may also be incorporated in the conventional straight through type of heat treating furnace.

As illustrated in FIG. 1, a furnace housing 12 which is of conventional construction is mounted on a frame that includes spaced legs 14. Located in the housing 12 of the furnace 10 is a heating chamber through which a muifle unit, generally indicated at 16, extends. Joined to the muflle unit 16 on the inlet end thereof is a flange 18, while a flange 20 is joined to the muflle unit on the discharge end thereof. Interconnected to the muifle unit 16 at the inlet end is an inlet duct generally indicated at 22 that includes a first inclined section 23 and a straight section 24 to which a flange 25 is joined that is bolted to the flange 18 of the muflle unit. Similarly, a discharge duct 26, which includes an inclined section 27 and a horizontal section 28 is joined to the mutfle unit 16 by a flange 29 that is interconnected to the flange 20 of the mufile unit. The discharge duct 26 also includes a second flange assembly 30 that interconnects the two sections 27 and 28.

The furnace 10 is of that type in which articles to be heattreated are continuously moved through the furnace heating chamber on a conveyor belt, which is indicated at 32 in FIG. 1. The conveyor belt 32 is conveniently driven by a motor (not shown) that is drivingly connected to a pulley 34 located at the entry end of the inlet duct 22. The belt 32 is also received on a pulley 36 located at the discharge end of the duct 26. The conveyor 32, which is preferably constructed of a wire mesh material is moved in the direction as indicated by the arrow in FIG. 1 and is designed to transfer thereon baskets having metal articles located therein into the heating chamber of the furnace for heat treatment thereof, the heat treated articles thereafter being discharged from the heating chamber as the conveyor moves the baskets into the discharge duct 26. As also shown in FIG. 1, any convenient support means is employed for mounting the pulleys 34 and 36 for rotation and are indicated as the support assemblies 38 and 40, respectively. A belt tensioning unit 42 is located at the discharge end of the duct 26 and is designed to shift the pulley 36 for tensioning the conveyor belt 32 as required.

A belt supporting tube 44 through which the conveyor belt 32 extends is further provided and extends lengthwise of the furnace construction below the housing thereof.

It is known that during the initial phase of the heating cycle, the mufile unit will tend to expand in the direction of the travel of the conveyor belt that extends therethrough. In order to compensate for the expansion of the mufiie unit and eventually for the contraction thereof, a plurality of roller assemblies are provided and are interconnected to the inlet and discharge ducts 22 and 26. Referring again to FIG. 1, the inlet and discharge ducts 22 and 26 are each provided with a plurality of roller assemblies that are mounted for rolling movement on track assemblies, as will now be described.

Depending from the sections 28 and 27 of the discharge duct 26 and joined thereto are pairs of spaced bars 46 and 48 and 50, 52, respectively. Rollers 54 are rotatably mounted on the lowermost ends of the spaced bars 46, while rollers 56 are similarly mounted on the lowermost ends of the bars 48. Mounted for rotation on the lowermost ends of the pairs of spaced bars 50 and 52 are rollers 58 and 60, respectively. -In order to accommodate the spaced rollers 54, 56, 58 and 60 for movement thereon, a track assembly is provided and as more clearly shown in FIG. 3 consists of spaced tracks 62. As seen in FIG. 3, the rollers 60 are mounted for rotation on a shaft 64 that is secured in the bars 52, the rollers 60 being grooved for rolling movement on the inverted V-shaped tracks 62. The tracks 62 are horizontally supported on spaced frame members 66 that are fixed in position on vertical standards 68. The frame members 66 are also joined to the legs 14 of the furnace housing and are fixed in aligned position for receiving the tracks 62 thereon. It is understood that the roller assemblies as represented by the bars 46 and rollers 54 mounted thereon, bars 48 and rollers 56 mounted thereon, and bars 50 and rollers 58 mounted thereon, are constructed similarly to the roller assemblies as represented by the bars 52 and rollers 60 mounted thereon and are mounted for movement on the tracks 62 as previously described in connection with the rollers 60.

As further illustrated in FIG. 1, the inlet duct 22 has a plurality of spaced bars 68, 70, 72 and 74 joined thereto in the manner as previously described for the bars 46, 48, 50 and 52. Joined to the lowermost ends of the spaced bars 68, 70, 72 and 74 are rollers 76, 78, 80 and 82, respectively. These latter rollers are received on spaced tracks 84 that are mounted on horizontal frame members 86 that are in turn supported by standards 88, 90, and 92. It is seen that as the mufile unit 16 expands and contracts during the operation of the furnace, the entire mufile assembly, which includes the mulfie 16, the inlet duct 22, and the discharge duct 26, will move longitudinally together as a unit and this movement is provided for by the rollers that are joined to the inlet discharge ducts and that are received on the tracks 62 and 84.

In order to prevent the inlet and discharge ducts from shifting vertically during expansion or contraction thereof and to further insure straight-line movement of the muflle assembly, reverse roller assemblies are provided for the inlet and discharge ducts and are indicated at 94 and 96 in FIGS. 1 and 3. Referring to FIG. 3, the reverse roller assembly 94 includes spaced bars 98 that project intermediate and below the frames 66 and have a shaft 100 joined thereto. Mounted for rotation on the shaft 100 is a roller 102 that is received on a reverse track 104. The reverse track 104 is secured to a plurality of spaced transverse members 106 that are joined to the frames 66. The reverse roller assembly 96 is constructed similarly to that just described and the roller assemblies 94 and 96 cooperate with the roller assemblies joined to the inlet and discharge ducts to provide for straight-line movement of the muflle assembly as it expands and contracts during the operation of the furnace.

In order to limit the longitudinal movement of the muflle unit 16 and the inlet and discharge ducts interconnected thereto, a stop construction is provided and is generally indicated at 108 in FIG. 2. The stop construction 108 is associated with the roller assembly 82 and, as shown, consists of brackets 110 and 112 through which adjustment screws 114 and 116, respectively, extend. Since the bar 74 has an L-shaped configuration, the adjustment screws 114 and 116 are appropriately spaced from the adjacent section of the bar 74, as illustrated in FIG. 2. Thus, the adjustment screw 116 defines a rear stop, while the adjustment screw 114 defines a forward stop, the stops limiting longitudinal movement of the inlet duct 22, discharge duct 26 and mufile unit 16 during the expansion or contraction of the mufile unit.

It is seen that the muffie unit 16 as joined to the inlet and discharge ducts is mounted for floating movement and as the mufiie grows or expands in response to the increase in temperature thereof during the heating cycle, the roller assemblies joined to the inlet and discharge ducts will move on their respective tracks and thus compensate for the expansion of the mufile unit. Since expansion or contraction of the muflle unit is normally in the direction of movement of the belt 32, the roller assemblies will compensate for this expansion and contraction and will prevent distortion of the muffle unit during the operation of the furnace.

While there is shown and described herein certain specific structure embodying the invention, it will be manifest to those skilled in the art that various modifications and rearrangements of the parts may be made without departing from the spirit and scope of the underlying inventive concept and that the same is not limited to the particular forms herein shown and described except insofar as indicated by the scope of the appended claims.

What is claimed is:

1. In a furnace construction, a base, a heating chamber mounted on said base in fixed position, a muffler extending through said heating chamber, an entry duct fixed to the mufiler on the inlet end thereof, a discharge duct fixed to the mufile 0n the discharge end thereof, a first roller assembly interconnected to said inlet duct, a first track assembly located adjacent to the entry duct and receiving said first roller assembly thereon, a second roller assembly inter-connected to said discharge duct, and a second track assembly located adjacent to the discharge duct and receiving said second roller assembly thereon, said roller assemblies being movable on said track assemblies with said inlet and discharge ducts and providing for a floating action of said mufile in said heating chamber thereby compensating for expansion and contraction of said mufiie during operation of said furnace construction, wherein said muffie is free to move forwardly and rearwardly in a longitudinal direction as it expands and contracts.

2. In a furnace construction as set forth in claim 1, said first roller assembly including at least a pair of spaced bars that are fixed to said inlet duct, a shaft mounted between said spaced bars and rollers rotatably mounted on said shaft and engaging spaced tracks of said first track assembly, said second roller assembly in cluding at least a pair of spaced bars that are fixed to said discharge duct, a shaft mounted between the bars that are fixed to the discharge duct, and rollers rotatably mounted on said shaft and engaging spaced tracks of said second track assembly.

3. In a furnace construction as set forth in claim 2, a stop member mounted on said first track assembly adjacent to said inlet duct and being engageable with a bar that is fixed to said inlet duct for limiting the longitudinal movement of said inlet duct when it moves in response to the expansion and contraction of said muflie.

4. In a furnace construction as set forth in claim 3, said roller assemblies including at least another pair of rollers spaced longitudinally of the first pair in each of the first and second roller assembly and engaging the first and second track assemblies.

5. In a furnace construction as set forth in claim 3, said first track assembly including a reversely positioned track located intermediate the spaced tracks of said first track assembly, a lower roller engaging said reversely positioned track and cooperating therewith to resist lifting forces exerted by said inlet duct and mufile due to expansion and contraction thereof during the operation of the furnace construction.

6. In a furnace construction as set forth in claim 5, said second track assembly including a reversely positioned track located intermediate the spaced tracks of said second track assembly, and a lower roller engaging the reversely positioned track of said second track assembly and cooperating therewith to resist lifting forces exerted by said discharge tube and mufiie due to expansion and contraction thereof during the operation of the furnace construction.

7. In a furnace construction as set forth in claim 1, a stop member mounted on said first track assembly adjacent to said inlet duct, and means fixed to said inlet duct and being engageable with said stop member for limiting the longitudinal movement of said inlet duct when it moves in response to the expansion and contraction of said muflle.

References Cited UNITED STATES PATENTS 2,061,910 11/1936 Kingston 263-8 2,468,456 4/1949 Ness 263-42 2,797,075 6/1957 Wilbur 263-8 2,825,547 3/1958 Vaughan 263-42 CHARLES J. MYHRE, Primary Examiner 

